TRE-CAMBRIAN LIFE 73 



seas, there may have been scope for various kinds 

 of living beings. The Grenville period is, however, 

 separated from the succeeding Huronian by a great 

 interval, occupied mainly by volcanic ejections and 

 earth-movements ; so that our Grenville series, if it 

 contains organic remains, may be supposed to afford 

 species differing from those of the Huronian, and 

 to form a sort of oasis in the desert of the early 

 pre-Cambrian world. We find that the limestones 

 of this age actually contain remains supposed to 

 be of animal origin. They were first found in 

 Canada, which contains the largest and best ex- 

 posed area of these rocks in the world, and were 

 brought under the notice of geologists by the late 

 Sir William E. Logan, the first director of the 

 Geological Survey of that country. 



In anticipation of details to be given later, the 

 story of this discovery and its announcement may 

 here be given in brief. 



As early as 1858, Sir William Logan had begun 

 to suspect that certain laminated bodies found in the 

 Laurentian limestones of the Grenville series might 

 be of organic origin. The points which struck him 

 were these : They differed from any known lamin- 

 ated concretions ; they resembled the *' Stromato- 



